1. Field of the Invention
The present invention relates to a noncontact charging device suitable for applying to a device used for charging portable devices, such as personal handy-phone systems (PHSs), personal digital assistants (PDAs), portable game devices, and notebook-sized personal computers. In particular, the present invention relates to a noncontact charging device designed to improve the safety of noncontact charging. Accordingly, a temperature-detecting unit detects a surface temperature of a primary coil (a coil on the side of the noncontact charging device) and when the surface temperature reaches a predetermined temperature or more, power transmission is terminated. In this case, the temperature-detecting unit for such detection is installed at a position when a foreign material, such as a metal, is placed on the noncontact charging device. The position is being adjusted depending on the size of the foreign material and the location thereof being placed.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2003-153457 (page 4, FIG. 3) discloses a noncontact charging device. According to the charging device, a device charged may be prevented from an increase in temperature while shortening a charging time. In addition, according to the charging device, an abnormal increase in temperature, when a foreign metal substance is placed on a charging portion, may be prevented.
The noncontact charging device has a temperature sensor which detects temperature of a power transmission coil. When the temperature detected by the temperature sensor is not more than a predetermined temperature, a charge control circuit controls a charging current to increase. In contrast, when the temperature detected by the temperature sensor exceeds the predetermined temperature, the charge control circuit controls a charging current to reduce.
Accordingly, when the temperature detected by the temperature sensor is low, a charging time can be reduced by increasing a charging current. In addition, if a foreign metal substance such as a coin is placed on a charging portion to increase the temperature of a power transmission coil, an abnormal increase in temperature of the foreign metal substance can be prevented from occurring by lowering the charging current.